None.
The present invention relates generally to mechanisms for infusing air from the atmosphere into bodies of water, and more particularly to such mechanisms which are powered by a rotary engine or motor and are provided with a rotating paddlewheel with its paddles extending below the water line thereby producing sprays of large volumes of water which absorb air from the atmosphere before falling back into the body of water.
With the advent of relatively strict governmental controls regarding the pollution of the environment, including the pollution of the nation""s water supply, sewage and wastewater treatment have become increasingly important. At one time it was customary for sewage to be dumped into any available water supply as a means of disposal. This practice is no longer tolerated. Now, sewage and other waste liquids must be treated before being released into a river or other water source.
Aeration is a widely used technique for treating a variety of fluids. For example, municipal water treatment plants, paper mills and drainage ponds all utilize aeration to continuously oxygenate and treat waste water. In wastewater treatment methods using aerobic or facultative waste stabilization lagoons, aeration of the wastewater is necessary to impart oxygen to the bacteria therein. These waste stabilization lagoons utilize aerobic and facultative bacteria to stabilize organic waste materials and clarify the water through consumption of organic matter. An adequate supply of oxygen to the body of water is essential in order for the bacteria to perform the stabilization function.
Aeration and mixing devices of various types are well known in the art. Known aeration systems include those which use air compressors to blow air into a waste stabilization lagoon, oxidation ditch, or equalization basin. However, these systems require extensive pipe work and labor-intensive monitoring and maintenance to prevent clogged air passages.
With waste water applications, the fluid to be aerated is maintained within one or more basins having large volume capacities, ranging from thousands to millions of gallons. Due to this large size, an aerator which can easily be moved to various locations within the basin is optimal. Float mounted aerators are designed to meet the aerating needs presented by large scale waste water holding basins.
One such float mounted aerator is described in U.S. Pat. No. 3,595,538 by Baumann, which discloses a liquid aerating paddlewheel rotor assembly which employs a support frame on which a rotor is rotationally mounted. The rotor rotates about a horizontal axis and has a plurality of mixing surfaces which lift, aerate, and mix the waste liquid. The rotor assembly is preferably mounted by a plurality of floats to float on top of the waste liquid. The rotor induces a flow in the liquid basin which provides for mixing of the liquid in conjunction with the aeration imparted to the liquid by the same rotor.
A number of problems are associated with the use of prior art aerators such as this one. First, in northern climates where the temperatures during the winter often fall below freezing for extended periods of time, it is not unusual for the surface of the basin to contain relatively large chunks of ice. In addition, it is also not unusual for wastewater basins to contain relatively large chunks of debris. The ice or other debris at the surface layer of liquid tends to jam the rotor. In extreme cases, this debris will break the rotor blades, thereby requiring replacement. The need to replace one or more rotor blades means that a certain amount of down time will be encountered during which the sewage treatment plant or process is inoperative. This down time can be significant in prior art designs in which each rotor blade is individually welded onto the axial shaft.
Moreover, it is important to be able to quickly and easily change the depth to which the paddleblades are immersed in the liquid in order to control the rate of aeration. In most prior art systems, such depth control requires specialized tools and involves a number of time consuming steps and adjustments.
Additionally, maintenance of the float mounted aerator, which most often takes place while the device is floating in a body of water, presents significant safety concerns. Normally, a maintenance worker is forced to either lean out of a boat to service the aerator, or attempt to balance on one of the rounded, slippery pontoons. Either approach is dangerous because of the possibility of slipping or falling. Thus, a design is needed which provides for ease of maintenance when the aerator is not floating in the water.
Moreover, the motor and drive mechanisms of prior art paddlewheel aerators are vulnerable to environmental damage by exposure to splashing water and debris. Thus, there exists a need for an efficient aerator which overcomes the disadvantages of prior art designs.
The invention is a paddlewheel aerator comprising a support structure, a drive mechanism contained within the support structure, a rotatable shaft extending horizontally from the drive mechanism; and a plurality of paddlewheels surrounding the shaft. A plurality of support legs are formed integrally with the support structure. In a preferred embodiment, a watertight drive box is positioned within the support structure. The drive box has a removable cover and a substantially water tight seal for preventing ingress of water. The drive box contains a motor drivably connected to the shaft. The motor is contained within an upper portion of the drive box so that the motor is positioned at a vertically elevated level compared to the shaft.